The overall objective of the proposed research is the specification and understanding of the development in children and adults of spatial representations of large environments (distal arrangements of landmarks). The research is conceptualized within a comparative-developmental framework proposed by Siegel & White (1975). Within this framework learning (i.e., qualitative and quantitative changes in behavior over diverse temporal spans) is construed as a development process. The proposed research focuses on the nature and development of visual-spatial knowledge of environmental landmarks and the construction of spatial representations from this knowledge. Within a recognition-in-context-memory paradigm, Ss are shown objects (slides, pictures, or in films) and asked to identify from an array both the object itself, and the context in which it had been presented originally. Studies are designed to specify the features of landmarks which get registered in memory and how these landmarks become integrated into an accurate representation of a route. Within a reconstruction of spatial layout paradigm, Ss are given a series of encounters (varying in exposure time and/or the nature of the encounter) with a spatial layout of landmarks and routes. Following each encounter Ss are instructed to build a replica of the layout (given a blank layout and identical elements). Studies are designed to specify the development of accurate cognitive maps (i.e., configurations) of spatial layouts. Both the development of landmark recognition and of layout construction in children and that in adults over shorter periods of time (e.g., over increasing exposure intervals and encounters) are being studied concomitantly.